The present invention relates to a freeze-picture transmission apparatus and, more particularly, to a freeze-picture transmission apparatus in which four video signals of four pictures are transmitted in a conventional one-picture video signal transmission period.
In a freeze-picture transmission apparatus according to the prior art, a carrier wave frequency-modulated or amplitude-modulated with a television video signal corresponding to a one field picture is transmitted through a narrow band public telephone line or a data communication line. In order to transmit a television signal on real time, the transmission line is required to have a bandwidth of about 5 MHz. However, the public telephone line transmits a signal only in a frequency band of 0.3 kHz to 3.4 kHz. In other words, the public telephone line only has a bandwidth of about 1.6 kHz at most. Therefore, it is necessary to convert the time axis of the video signal for transmission through the narrow band public telephone line. The time axis conversion takes 42 seconds for transmitting the one television signal corresponding to the field picture through the public telephone line. Such a long conversion time period of 42 seconds is a disadvantage of the prior art freeze-picture transmission apparatus. Another disadvantage is the difficulty in observing many field pictures simultaneously at a reception end.